Polymeric composite materials that contain organic and/or inorganic filler materials have become desirable for a variety of uses because of their excellent mechanical properties and weathering stability. Foamed versions of these materials can have a relatively low density yet the filler materials can provide a composite material that is extremely strong. The polymer provided in the composite material can help provide good toughness (i.e., resistance to brittle fracture) and resistance to degradation from weathering to the composite when it is exposed to the environment. Thus, polymeric composite materials including organic and/or inorganic fillers can be used in a variety of applications, including in building materials.
Recently, there has been an increased interest in using fly ash as a filler in polymer composites. Fly ash has attracted attention as a filler for several reasons. First, fly ash is a by-product produced during the combustion of coal. As such, fly ash qualifies as a recycled material, making it an environmentally friendly choice for use as a filler in composites. Fly ash is also relatively inexpensive when compared to alternative fillers often used in polymer composites. Furthermore, fly ash can be incorporated in polymer composites without adversely impacting their resultant mechanical properties. In fact, in some cases, fly ash can improve the mechanical properties of polymer composites.
When using fly ash to form polymer composites, difficulties arise in producing composites having consistent batch-to-batch materials properties (e.g., consistent hardness). Depending on its combustion history, fly ash can have varied chemical and physical properties. For example, fly ash obtained from different sources can include varying quantities of residual organic carbon. The residual organic carbon can absorb organic molecules (e.g., polymerization catalysts used to cure the polymer composite), influencing the properties of the resultant polymer composites. Methods for addressing the variation in fly ash performance offer the potential to provide polymeric composites having consistent batch-to-batch materials properties.